Embodiments of the invention pertain generally to systems or methods used to control a vehicle traveling along a route. Other embodiments of the invention pertain to such systems that may be used on locomotives in a train traveling on a railroad track.
Systems and methods for developing a trip plan for vehicle assets such as locomotives and trains have been disclosed, and are designed for operating the locomotives at optimal speeds and power settings while minimizing fuel consumption and/or emissions. For example, in the commonly owned published application U.S. Publication No. 2007-0219680-A1 (incorporated by reference herein in its entirety) there is disclosed a method and closed loop system for optimizing a train trip using speed signal information, which is also schematically illustrated in FIG. 1. In such a system, data relative to locomotive/train characteristics and railroad track systems are used to generate a trip plan. Such input information includes, but is not limited to, train position, consist composition (such as locomotive models), locomotive tractive power performance of locomotive traction transmission, consumption of engine fuel as a function of output power, cooling characteristics, intended trip route (effective track grade and curvature as function of milepost or an “effective grade” component to reflect curvature, following standard railroad practices), car makeup and loading (including effective drag coefficients), desired trip parameters including, but not limited to, start time and location, end location, travel time, crew (user and/or operator) identification, crew shift expiration time, and trip route. Based on the specification data input, an optimal trip plan that minimizes fuel use and/or generated emissions subject to speed limit constraints and a desired start and end time is computed to produce a trip profile. The profile contains the optimal speed and power (e.g., notch/throttle) settings for the train to follow, expressed as a function of distance and/or time from the beginning of the trip, train operating limits (including but not limited to, the maximum notch power and brake settings), speed limits as a function of location, and the expected fuel used and emissions generated.
In such a system and during the course of a trip, the actual speed of the locomotive is monitored and compared to the trip plan, which includes data relative to the optimal speed of the locomotive at various positions on the track. If the locomotive is not operating at the optimal speed, or within a range of the optimal speed according to the trip plan, the speed is adjusted either manually or by an automated controller. In addition, the trip plan may be changed during the course of executing a planned trip. That is, events during daily operations may motivate the generation of a new or modified plan, including a new or modified trip plan that retains the same trip objectives, for example, when a train is not on schedule for a planned meet or pass with another train and therefore must make up the lost time.
Using the actual speed, power, and location of the locomotive, a planned arrival time is compared with a currently estimated (predicted) arrival time. Based on a difference in the times, as well as the difference in parameters (detected or changed by dispatch or the operator), the plan is adjusted. This adjustment may be made automatically responsive to a railroad company's policy for handling departures from plan, or manually as the on-board operator and dispatcher jointly decide the best approach for returning to plan. However, such systems may factor in an error of about 1 mph (about 1.609 kilometers/hour) in the detection of the actual speed, and/or may accept a 1 mph (1.609 kilometers/hour) difference in the actual speed and planned speed. Therefore, over a sustained period, if the speed error is accepted without adjusting the speed the train may not reach destinations or intermediate points of interest at estimated arrival times.